Since there is no straightforward way to determine the real speed value when there is no speed feedback, monitoring the speed of a fan can in fact become complicated. Here are a few workable options:
A tiny optical marker can be attached to the fan blade, and a photoelectric sensor or encoder can then be placed close to the fan. This allows the photoelectric sensor to detect changes in light as the fan blades pass through, count the number of times they do so, and determine the fan speed.
Hall sensor: By detecting changes in the magnetic field, the hall sensor can gauge the rotation of the fan blades. You may set up a small magnet on the fan blade, and then place one or more change Hall sensors next to the fan. When the blade rotates, the magnet passes through the sensors and generates signals, which can be used to calculate the fan speed.
Sound frequency: When the fan rotates, it produces noise, and the frequency of the noise is related to the fan speed. You can use a sensor or microphone to capture the sound generated by the fan, convert the captured sound signal into frequency, and then detect audio changes in the main frequency. The accuracy of this method may be relatively low, as noise is influenced by the environment and fan design.
Vibration sensor: The rotation of the fan generates vibration, and the frequency of the vibration can be used to estimate the speed of the fan. Installing a vibration sensor near the fan can detect the vibration caused by the rotation of the blades, and then estimate the fan speed by analyzing the vibration data collected by the sensor.
The above are some methods for measuring fan speed, but the accuracy of these methods may be affected by environmental factors, sensor performance, and fan design, so sufficient testing and verification are required before practical application.
